The rear trunnion is not a countable part. It is actually a "stock tang", not a trunnion.

However, there are US made ones available though, if you would prefer one.

A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, IS BEING infringed.
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Says New York "... and failing to safely store a weapon could lead to a misdemeanor charge". W. T. F.